Dual Diameter Sizer, type -H
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Catalog No.: DDS-1-H
Shipping Weight: 1.50 pounds
The Dual Diameter Sizer die looks like a core seater but it has
two internal diameters, usually the difference between the
rifling diameter (distance from groove to groove across the
bore) and the bore diameter (which would be the distance across
the lands from one side to the other of the bore). In most
modern guns this is .008 inches, allowing for rifling depth
of .004 inches.
The purpose of the die is to reduce part of a finished bullet
diameter, usually the nose, so that it fits on top of the
rifling and does not engage it. The distance you push the
bullet into the die controls how long of a section is reduced
to this "minor" diameter.
The rest of the bullet is left the same size, so you specify
the DDS-1-H with two numbers: the caliber is the major
diameter, and it is the same as the caliber of the point
forming die used to make that bullet. The reduced section
is specified as a minor diameter. The length of the reduced
section is up to you, but you should allow a "driving band"
to remain at full diameter, probably about a caliber length but
certainly as much as you will be seating into the neck of
Dual Diameter Sizer dies have two other specifications.
The base punch, which is the external one, must match the
shape of the bullet base. There probably will not be
enough force involved to reshape the base in this step,
so it is best to match the bullet base and punch shape
rather than attempting to change it here.
The other specification is the nose shape. This is
important, as the force required to push the bullet back
out of the die, after sizing it down so much, is enough
to deform the nose unless you use the same shape of cavity
in the internal punch as the original bullet nose.
However, one small advantage is that if you intend to
make a lead tipped dual diameter bullet, you can do away
with the lead tip forming die. The pressure of pushing
the drawn bullet back out of the die is enough to also re-
shape the lead tip, so it does not have to be preformed in
any way. It just needs to be large enough to fill in the
volume required and not leave a void at the tip. Surplus
lead which projects from the bullet tip will probably be
smoothed into a thin film that lays on top of the bullet
nose, and can be peeled off with a fingernail. Once you
find the proper amount of projecting lead tip, you will
have neither a void nor any film of lead pushed over the
DDS-1-H dies have also been used to form a heel base, by
designing the punches so that you push the bullet backward
into the die and reduce the rear portion. This means the
external punch would be shaped to support the nose of
the bullet, and the internal punch would match the base
shape (usually flat, but could be cup or hollow).